1. Field of the Invention
The present invention relates to a vibration sound reducing device including a vibration absorbing means which is mounted to a passage defining structure for defining a liquid passage faced by at least a portion of a vibration generating section, and which is adapted to absorb a vibration transmitted from the vibration generating section through a liquid in the liquid passage. Particularly, the present invention relates to a vibration sound reducing device appropriately applied to a water-cooled internal combustion engine in which a cooling water passage including a water passage portion surrounding a cylinder portion as the vibration generating section is provided in an engine body.
2. Description of the Related Art
To reduce a piston slap sound caused by collision of a piston against an inner surface of the cylinder portion in a water-cooled internal combustion engine, the following techniques have been conventionally used: (1) a technique to suppress the amplitude of vibration to a small level by increasing the thickness of the cylinder portion; and (2) a technique to suppress the amplitude of vibration to a small level by increasing the thickness of an outer wall of a cylinder block.
Known structures for suppressing the vibration of non-compressable cooling water existing in a cooling water passage, include, for example, (3) a structure in which a sound shielding layer is provided outside the cooling water passage in the cylinder block with a partition wall interposed therebetween, as disclosed in Japanese Utility Model Application Laid-open No. 53-68814.
In the techniques (1) and (2), however, the weight of the engine body is increased due to the increase in thickness of the cylinder portion and the cylinder block. The structure (3) is a double, structure in which the cooling water passage and the sound layer are disposed through the partition wall interposed therebetween. Therefore, the structure (3) is complicated and is difficult to manufacture, resulting in an increased manufacture cost, and bringing about an increase in weight of the engine body.
Therefore, the present assignee has already proposed a vibration sound reducing device for a water-cooled internal combustion engine in Japanese Patent Application No. 8-351288, comprising a vibration absorbing means which is mounted to an outer wall of an engine body so as to occlude a through-bore that is provided in the outer wall of the engine body while facing a cooling water passage, the vibration absorbing means including an elastic membrane with one surface thereof facing the cooling water passage and with the other surface thereof facing a space.
With this proposed technique, a variation in pressure of the cooling water is absorbed by flexing of the elastic membrane with one surface thereof facing the cooling water passage. Thus, an exciting force applied from the cooling water to the outer wall of the engine body can be effectively reduced, and the piston slap sound radiated from the engine body can be reduced without an increase in weight of the engine body.
In the above proposed technique, however, a peripheral edge of the elastic membrane is secured by baking or the like to a member that is mounted to the engine body so as to occlude the through-bore. In such a structure in which the elastic membrane is fixed, it is difficult to ensure the satisfactory sealing between the cooling water passage and the space due to the water pressure in the cooling water passage or due to the deterioration of the elastic membrane. It is also considered that the peripheral edge of the elastic membrane is adhered to the member mounted to the engine body, but even in this case, it is difficult to ensure the satisfactory sealing property.
Accordingly, it is an object of the present invention to provide a vibration sound reducing device, wherein the vibration sound such as the piston slap sound can be effectively reduced in a simple structure which brings about no increase in weight of the passage defining structure and moreover, the satisfactory sealing can be ensured.
To achieve the above object, according to a first aspect and feature of the present invention, there is provided a vibration sound reducing device comprising a vibration absorbing means which is mounted to a passage defining structure defining a liquid passage faced by at least a portion of a vibration generating section, the vibration absorbing means absorbing the vibration transmitted from the vibration generating section through a liquid in the liquid passage, wherein the vibration absorbing means comprises an occluding member mounted to an outer wall of the passage defining structure so as to occlude a through-bore which is provided in the outer wall of the passage defining structure and opens at an inner end thereof into the liquid passage, an elastic membrane with one of opposite surfaces thereof facing the liquid passage and with the other surface thereof facing a space defined between the elastic membrane and the occluding member, and a retaining member mounted to the occluding member for retaining the elastic membrane between the retaining member and the occluding member.
With such arrangement of the first feature, the vibration generated in the vibration generating section induces the vibration of the liquid in the liquid passage, but a variation in pressure of the liquid is absorbed by flexing of the elastic membrane with its one surface facing the liquid passage. Thus, the exciting force applied from the liquid to the passage defining structure is effectively reduced, and the vibration sound radiated from the passage defining structure is reduced. Moreover, the vibration absorbing means is mounted to a portion of the outer wall of the passage defining structure and hence, the increase in weight of the passage defining structure due to the mounting of the vibration absorbing means can be suppressed to a small level to the utmost. In addition, the elastic membrane is retained between the occluding member and the retaining member. Therefore, it is possible to avoid that the sealability is reduced due to the liquid pressure in the liquid passage or due to the deterioration of the elastic membrane, whereby the elastic membrane can be reliably retained between the occluding member and the retaining member. As compared with a vibration absorbing means including an elastic membrane secured directly to an occluding member by baking or adhesion, the sufficient sealability can be ensured.
According to a second aspect and feature of the present invention, in addition to the arrangement of the first feature, the occluding member has a cylindrical mounting portion projectingly provided at an inner end thereof; the elastic membrane includes an endless sealing portion which is in contact with a tip end face of the mounting portion, and a membrane portion formed at a thickness smaller than that of the sealing portion and integrally connected to an inner periphery of the sealing portion with a step formed therebetween; and the retaining member mounted to the occluding member with the sealing portion sandwiched between the retaining member and the tip end of the mounting portion is provided with a positioning portion which is engaged with the inner periphery of the sealing portion to position the elastic membrane in a plane perpendicular to an axis of the mounting portion. With such arrangement of the second feature, the sealing portion of the elastic membrane is accurately positioned and sandwiched between the mounting portion and the retaining member, whereby the sealability can be more sufficiently ensured to enhance the vibration absorbing characteristic.
According to a third aspect and feature of the present invention, in addition to the arrangement of the first feature, the occluding member has a cylindrical mounting portion projectingly provided at an inner end thereof; the elastic membrane includes an endless sealing portion which is in contact with a tip end face of the mounting portion, and an annular lip portion protruding outwards from an outer periphery of the sealing portion; and the retaining member mounted to the occluding member with the sealing portion sandwiched between the retaining member and the tip end of the mounting portion is provided with a cylindrical portion which comes into contact with the outer periphery of the lip portion to position the elastic membrane in a plane perpendicular to an axis of the mounting portion. With such arrangement of the third feature, the sealing portion of the elastic membrane is accurately positioned and sandwiched between the mounting portion and the retaining member, whereby the sealability can be more sufficiently ensured to enhance the vibration absorbing characteristic. Moreover, a flash produced on the outer periphery of the elastic membrane upon formation of the elastic membrane by molding can be effectively utilized as the lip portion, and hence, a flash removing operation after formation of the elastic membrane is not required.
According to a fourth aspect and feature of the present invention, in addition to the arrangement of the first feature, the retaining member is press-fitted over the occluding member with an outer periphery of the elastic membrane sandwiched between the retaining member and the occluding member, and the occluding member is provided with a limiting portion for limiting an end of movement of the retaining member in a direction of press-fitting over the occluding member. With such arrangement of the fourth feature, it is possible to reliably retain the elastic membrane on the occluding member. In addition, since the retaining member may be press-fitted, until the press-fitting of the retaining member is limited by the limiting portion, the sealability of the elastic membrane can be sufficiently ensured, while enhancing the press-fitting operability.
According to a fifth aspect and feature of the present invention, in addition to the arrangement of the first feature, the occluding member is provided with an annular engage portion which is engaged with the elastic membrane over an entire periphery of the elastic membrane to position the elastic membrane in a plane perpendicular to an axis of the through-bore. With such arrangement of the fifth feature, the sealing portion of the elastic membrane is accurately positioned and sandwiched between the mounting portion and the retaining member, whereby the sealability can be more sufficiently ensured to enhance the vibration absorbing characteristic.
According to a sixth aspect and feature of the present invention, in addition to the arrangement of the first feature, the vibration generating section is a cylinder portion which is provided in a cylinder block in a water-cooled internal combustion engine, said cylinder portion having a piston slidably received therein, and the passage defining structure including the cylinder block is an engine body which is provided with (1) a cooling water passage defined as the liquid passage including a water passage portion surrounding the cylinder portion, and (2) the vibration absorbing means for absorbing the vibration transmitted from the cylinder portion through the cooling water in the cooling water passage. With such arrangement of the sixth feature, the vibration of the cylinders caused by collision of the piston against an inner surface of each of the cylinders induces the vibration of the cooling water in the cooling water passage. However, a variation in pressure of the cooling water is absorbed by flexing of the elastic membrane with its one surface facing the cooling water passage. Therefore, an exciting force applied from the cooling water to the outer wall of the engine body is effectively reduced, and a piston slap sound radiated from the engine body is reduced. Moreover, since the vibration absorbing means is mounted to a portion of the outer wall of the engine body, the increase in weight of the engine body due to the mounting of the vibration absorbing means can be suppressed to a small level to the utmost.
According to a seventh aspect and feature of the present invention, there is provided a vibration reducing device comprising a vibration absorbing means which is mounted in a passage defining structure defining a liquid passage faced by at least a portion of a vibration generating section, the vibration absorbing means absorbing the vibration transmitted from the vibration generating section through a liquid in the liquid passage, wherein the vibration absorbing means comprises an occluding member which is mounted to an outer wall of the passage defining structure so as to occlude a through-bore which is provided in the outer wall and opens at an inner end thereof into the liquid passage, and an elastic membrane press-fitted over and fixed to the occluding member with one of opposite surface thereof facing the liquid passage and the other surface thereof facing a space defined between the elastic membrane and the occluding member.
With such arrangement of the seventh feature, the vibration generated in the vibration generating section induces the vibration of the liquid in the liquid passage. However, a variation in pressure of the cooling water is absorbed by flexing of the elastic membrane with its one surface facing the cooling water passage. Therefore, an exciting force applied from the liquid to the passage defining structure is effectively reduced, and a piston slap sound radiated from the passage defining structure is reduced. Moreover, since the vibration absorbing means is mounted to a portion of the outer wall of the engine body, the increase in weight of the passage defining structure due to the mounting of the vibration absorbing means can be suppressed to a small level to the utmost. In addition, the elastic membrane is press-fitted over and fixed to the occluding member. Therefore, it is possible to avoid that the sealability is reduced due to the liquid pressure in the liquid passage or due to the deterioration of the elastic membrane, thereby reliably maintaining the fixed state of the elastic membrane to the occluding member. As compared with the vibration absorbing means including the elastic membrane secured to the occluding member by baking or adhesion, the sufficient sealability can be ensured.
According to an eighth aspect and feature of the present invention, in addition to the arrangement of the seventh feature, the occluding member has a cylindrical mounting portion projectingly provided at an inner end thereof, and the elastic membrane includes a cylindrical sealing portion press-fitted over an outer periphery of the mounting portion, and a membrane portion connected to an end of the sealing portion to define a space between the membrane portion and the occluding member, the sealing portion being provided with a ring-shaped reinforcing member. With such arrangement of the eighth feature, during press-fitting of the elastic membrane over the occluding member, the cylindrical shape of the sealing portion can be maintained by reinforcing the sealing portion of the elastic membrane, i.e., a portion press-fitted over the occluding member with the reinforcing member, thereby facilitating the press-fitting operation, and reliably maintaining the close contact of the sealing portion with the outer periphery of the mounting portion to enhance the sealability.
According to a ninth aspect and feature of the present invention, in addition to the arrangement of the eighth feature, the reinforcing member is mounted within the sealing portion in such a manner that the reinforcing member is entirely wrapped with the sealing portion. With such arrangement, it is possible to reliably prevent the reinforcing member from being fallen from the elastic membrane.
According to a tenth aspect and feature of the present invention, in addition to the arrangement of the eighth feature, the elastic membrane is provided with a slip-off preventing portion which is resiliently engaged with the occluding member for inhibiting the elastic membrane from falling off the occluding member. Thus, it is possible to reliably maintain the press-fitted and fixed state of the elastic membrane to the occluding member.
According to an eleventh aspect and feature of the present invention, in addition to the arrangement of the seventh feature, a sealing portion of the elastic membrane is provided with a slip-off preventing portion which is resiliently engaged with a mounting portion of the occluding member for inhibiting the elastic membrane from falling off the mounting portion, the slip-off preventing portion being located inside the reinforcing member. Thus, it is possible to firmly maintain the engagement of the slip-off preventing portion with the mounting portion by the reinforcing member.
According to a twelfth aspect and feature of the present invention, in addition to the arrangement of the seventh feature, the occluding member has a cylindrical mounting portion projectingly provided at an inner end thereof, and the elastic membrane includes a cylindrical sealing portion press-fitted over an outer periphery of the mounting portion, and a membrane portion connected to an end of the sealing portion to define a space between the membrane portion and the occluding member, the thickness of the sealing portion being set larger than that of the membrane portion. Thus, the rigidity of the sealing portion can be increased to a relatively high level by forming the sealing portion at the relatively large thickness, thereby firmly maintaining the press-fitted state of the sealing portion over the mounting portion.
According to a thirteenth aspect and feature of the present invention, in addition to the arrangement of the seventh feature, the vibration generating section is a cylinder portion which is provided in a cylinder block in a water-cooled internal combustion engine, the cylinder portion having a piston slidably received therein, and the passage defining structure including the cylinder block is an engine body which is provided with (1) a cooling water passage defined as the liquid passage including a water passage portion surrounding the cylinder portion, and (2) the vibration absorbing means for absorbing the vibration transmitted from the cylinder portion through the cooling water in the cooling water passage.
With such arrangement of the thirteenth feature, the vibration of the cylinders caused by collision of the piston against an inner surface of each of the cylinders induces the vibration of the cooling water in the cooling water passage. However, a variation in pressure of the cooling water is absorbed by flexing of the elastic membrane with its one surface facing the cooling water passage. Therefore, an exciting force applied from the cooling water to the outer wall of the engine body is effectively reduced, and a piston slap sound radiated from the engine body is reduced. Moreover, since the vibration absorbing means is mounted to a portion of the outer wall of the engine body, the increase in weight of the engine body due to the mounting of the vibration absorbing means can be suppressed to a small level to the utmost.
According to a fourteenth aspect and feature of the present invention, there is provided a vibration sound reducing device comprising a vibration absorbing means which is mounted in a passage defining structure defining a liquid passage faced by at least a portion of a vibration generating section, the vibration absorbing means absorbing the vibration transmitted from the vibration generating section through a liquid in the liquid passage, wherein the passage defining structure is provided at an outer wall thereof with a through-bore which opens at an inner end thereof into the liquid passage, and a collar-shaped receiving portion protruding radially inwards from an inner surface of the through-bore, and the vibration absorbing means comprises an occluding member mounted to the outer wall to occlude the through-bore, and an elastic membrane having an outer periphery clamped between the receiving portion and the occluding member with one of opposite surfaces thereof facing the liquid passage and the other surface thereof facing a space defined between the elastic membrane and the occluding member.
With such arrangement of the fourteen feature, the vibration generated in the vibration generating section induces the vibration of the liquid in the liquid passage. However, a variation in pressure of the liquid is absorbed by flexing of the elastic membrane with its one surface facing the liquid passage. Therefore, an exciting force applied from the liquid to the outer wall of the passage defining structure is effectively reduced, and a vibration sound radiated from the passage defining structure is reduced. Moreover, since the vibration absorbing means is mounted to a portion of the outer wall of the passage defining structure, the increase in weight of the passage defining structure due to the mounting of the vibration absorbing means can be suppressed to a small level to the utmost. In addition, the elastic membrane is clamped between the receiving portion provided at the outer wall of the passage defining structure and the occluding member, and hence, it is possible to avoid that the sealability is reduced due to the liquid pressure in the liquid passage or due to the deterioration of the elastic membrane, thereby reliably clamping the elastic membrane between the occluding member and the receiving portion. As compared with the vibration absorbing means including the elastic membrane secured directly to the occluding member by baking or adhesion, the sufficient sealability can be ensured. Further, the flowing of the liquid in the liquid passage can be prevented from being hindered, by providing the elastic membrane, so that it does not protrudes into the liquid passage. In addition, since the space cannot be surrounded by the liquid in the liquid passage, it is possible avoid that the vibration characteristic is changed due to a variation in temperature of the liquid, whereby the vibration characteristic is stabilized.
According to a fifteenth aspect and feature of the present invention, in addition to the arrangement of the fourteenth feature, the outer wall of the passage defining structure is integrally provided with a cylindrical boss portion having the through-bore; the outer periphery of the elastic membrane clamped between the receiving portion and the occluding member is provided with a protruding annular lip which is in close contact with the receiving portion of the occluding member; and the occluding member is integrally provided with a limiting collar portion which is in contact with an outer end of the boss portion to limit an end of movement of the occluding member in a direction toward the receiving portion. With such arrangement of the fifteenth feature, the sealability can be enhanced by crushing the lip, and the crushing margin of the lip can be set at a preset value by the abutment of the limiting collar portion against the outer end of the boss portion. It is not necessary to attach the occluding member to the outer wall, while taking the margin of crushing of the lip into consideration, thereby enhancing the assemblability.
According to a sixteenth aspect and feature of the present invention, in addition to the arrangement of the fourteenth feature, the outer periphery of the elastic membrane is provided with an engage portion which is engaged with the occluding member. With such arrangement of the sixteenth feature, it is possible not only to reliably prevent the elastic membrane from falling from between the receiving portion and the occluding member, but also to mount the vibration absorbing means to the outer wall of the passage defining structure in a state in which the elastic membrane is mounted to the occluding member, and hence, the assembling operation is facilitated.
According to a seventeenth aspect and feature of the present invention, in addition to the arrangement of the sixteenth feature, the occluding member is provided with a cylindrical portion which clamps the outer periphery of the elastic membrane between the cylindrical portion and the receiving portion, and the outer periphery of the elastic membrane is integrally provided with an engage portion which is formed into a cylindrical shape, so that the engage portion is resiliently fitted into an annular recess which is provided in an outer periphery of a tip end of the cylindrical portion in the annular recess having a tapered shape with its diameter reduced toward the receiving portion. With such arrangement of the seventeenth feature, the cylindrical portion of the occluding member can be fitted to the engage portion, while avoiding a damage to the elastic membrane, thereby facilitating the mounting of the elastic membrane to the occluding member. Moreover, in a state in which the cylindrical portion is fitted to the engage portion, the elastic membrane exhibits a resilient force for bringing the inner surface of the engage portion into close contact with the annular recess and hence, the inner surface of the engage portion can be brought into close contact with the entire surface of the annular recess to further enhance the sealing property.
According to a eighteenth aspect and feature of the present invention, in addition to the arrangement of the fourteenth feature, the vibration generating section is a cylinder portion which is provided in cylinder block in a water-cooled internal combustion engine, the cylinder portion having a piston slidably received therein; the passage defining structure is an engine body which includes the cylinder block and which is provided with a cooling water passage defined as the liquid passage including a water passage portion surrounding the cylinder portions; and the vibration absorbing means is mounted to the outer wall of the engine body for absorbing the vibration transmitted from the cylinder portions through the cooling water in the cooling water passage. With such arrangement of the eighteenth feature, the vibration of each of the cylinders caused by collision of the piston against the inner surface of the cylinder induces the vibration of the cooling water in the cooling water passage, but a variation in pressure of the cooling water is absorbed by flexing of the elastic membrane with its one surface facing the cooling water passage. Therefore, the exciting force applied from the cooling water to the outer wall of the engine body is effectively reduced, and a piston slap sound radiated from the engine body is reduced. Moreover, the vibration absorbing means is mounted to a portion of the outer wall of the engine body and hence, the increase in weight of the engine body due to the mounting of the vibration absorbing means can be suppressed to a small level to the utmost.
According to a nineteenth aspect and feature of the present invention, there is provided a vibration sound reducing device comprising a vibration absorbing means which is mounted to a passage defining structure defining a liquid passage faced by at least a portion of a vibration generating section, the vibration absorbing means absorbing the vibration transmitted from the vibration generating section through a liquid in the liquid passage, wherein the vibration absorbing means comprises an occluding member mounted to an outer wall of the passage defining structure so as to occlude a through-bore which is provided in the outer wall of the passage defining structure and opens at an inner end thereof into the liquid passage, and an elastic membrane mounted to the occluding member with opposite surfaces thereof facing the liquid passage and a space defined between the elastic membrane and the occluding member, the elastic membrane being of such a shape that it is curved toward the occluding member, immediately before it comes into contact with at least the occluding member, when the elastic membrane is mounted to the occluding member.
With such arrangement of the nineteenth feature, the vibration generated in the vibration generating section induces the vibration of the liquid in the liquid passage, but a variation in pressure of the liquid is absorbed by flexing of the elastic membrane with its one surface facing the liquid passage. Thus, the exciting force applied from the liquid to the passage defining structure is effectively reduced, and the vibration sound radiated from the passage defining structure is reduced. Moreover, the vibration absorbing means is mounted to a portion of the outer wall of the passage defining structure and hence, the increase in weight of the passage defining structure due to the mounting of the vibration absorbing means can be suppressed to a small level to the utmost. There is a possibility that the elastic membrane may be expanded toward the liquid defining structure due to an increase in pressure in the space defined between the elastic membrane and the occluding member, when the elastic membrane is mounted to the occluding member, thereby changing the vibration characteristic of the elastic membrane to reduce the vibration absorbing effect. There is also a possibility that the flowing of the liquid in the liquid passage may be hindered, when the elastic membrane is expanded in a large amount toward the liquid defining passage. However, since the elastic membrane is of the shape such that it is curved toward the occluding member, immediately before it comes into a contact with at least the occluding member, when the elastic membrane is mounted to the occluding member, it is possible to avoid that the elastic membrane is expanded toward the liquid defining passage by the mounting of the elastic membrane to the occluding member, and to provide an excellent vibration absorbing effect. Additionally, the flowing of the liquid in the liquid passage cannot be hindered.
According to a twentieth aspect and feature of the present invention, in addition to the arrangement of the nineteenth feature, the occluding member has a cylindrical mounting portion projectingly provided at an inner end thereof and the elastic membrane is formed into a cap-shape and comprises a cylindrical sealing portion fitted over and fixed to an outer periphery of the mounting portion, and a membrane portion connected to an end of the sealing portion while defining a space between the membrane portion and the occluding member. With such arrangement of the twentieth feature, by fitting and fixing the sealing portion to the cylindrical mounting portion, the mounting of the elastic membrane to the occluding member can be facilitated, and the area of contact between the elastic membrane and the occluding member can be increased to enhance the sealability between the elastic membrane and the occluding member. Moreover, at a time point when a tip end of the sealing portion is fitted over the mounting portion of the occluding member upon the mounting of the elastic membrane to the occluding member, the space is brought into a closed state. As the degree of fitting of the sealing portion over the mounting portion is increased, the pressure in the space is largely increased. However, since the elastic membrane is of the shape such that it is curved toward the occluding member before mounting of the elastic membrane to the occluding member, it is possible to further effectively prevent the elastic membrane from being expanded toward the liquid passage by the mounting the elastic membrane to the occluding member, notwithstanding that the pressure in the space is largely increased.
According to a twenty-first aspect and feature of the present invention, in addition to the arrangement of the nineteenth feature, the elastic membrane is formed into a shape such that it is expanded toward the occluding member in a natural state with no external force applied thereto. With such arrangement of the twenty-first feature, it is possible to prevent the elastic membrane from being expanded toward the liquid passage by the mounting of the elastic membrane to the occluding member without application of any operation when the elastic membrane is mounted to the occluding member.
According to a twenty-second aspect and feature of the present invention, in addition to the arrangement of the nineteenth feature, the elastic membrane is assembled to the occluding member in a state in which the elastic membrane is urged by an urging member, so that it is curved toward the occluding member. With such arrangement of the twenty-second feature, since the elastic membrane is assembled to the occluding member in the state in which the elastic membrane is forcibly curved toward the space, it is possible to avoid that the pressure in the space is largely increased, by eliminating air at that portion of the elastic membrane which is curved toward the space.
According to a twenty-third aspect and feature of the present invention, there is provided a vibration sound reducing device comprising a vibration absorbing means which is mounted to a passage defining structure defining a liquid passage faced by at least a portion of a vibration generating section, the vibration absorbing means absorbing the vibration transmitted from the vibration generating section through a liquid in the liquid passage, wherein the passage defining structure is provided at an outer wall thereof with a mounting bore which opens at its inner end into the liquid passage, and the vibration absorbing means comprises an occluding member mounted to occlude the mounting bore and including a cylindrical support tube portion having external threads provided around an outer periphery thereof and threadedly engaged with internal threads provided on an inner surface of the mounting bore, and an elastic membrane mounted to an inner end of the occluding member with one of opposite surfaces thereof facing the liquid passage and the other surface thereof facing a space defined between the elastic membrane and the occluding member, the occluding member being provided with a tool-engaging bottomed bore which opens into an outer end of the occluding member, the tool-engaging bore being defined to have an axially extending portion disposed in the support tube portion within an axial region where the external threads are disposed.
With such arrangement of the twenty-third feature, the vibration generated in the vibration generating section induces the vibration of the liquid in the liquid passage, but a variation in pressure of the liquid is absorbed by flexing of the elastic membrane with its one surface facing the liquid passage. Thus, the exciting force applied from the liquid to the passage defining structure is effectively reduced, and the vibration sound radiated from the passage defining structure is reduced. Moreover, the vibration absorbing means is mounted to a portion of the outer wall of the passage defining structure and hence, the increase in weight of the passage defining structure due to the mounting of the vibration absorbing means can be suppressed to a small level to the utmost. In addition, since the occluding member is provided with the tool-engaging bore which opens into the outer end thereof, the occluding member can be screwed into the mounting bore by bringing a tool into engagement into the tool-engaging bore to turning the occluding member. Moreover, since the axially extending portion of the tool-engaging bore is disposed within the axial region where the external threads are disposed, it is possible to avoid, to the utmost, that the portion for engagement of the tool is disposed at a location axially offset from the support tube portion, thereby making the occluding member compact, and reducing the weight of the occluding member by an amount corresponding to the provision of the tool-engaging bore.
According to a twenty-fourth aspect and feature of the present invention, there is provided a vibration sound reducing device comprising a vibration absorbing means which is mounted to a passage defining structure defining a liquid passage faced by at least a portion of a vibration generating section, the vibration absorbing means absorbing the vibration transmitted from the vibration generating section through a liquid in the liquid passage, wherein an outer wall of the passage defining structure is provided with a mounting bore which opens at an inner end thereof into the liquid passage, and the vibration absorbing means comprises an occluding member which is mounted to occlude the mounting bore and which includes a cylindrical support tube portion having external threads provided around an outer periphery thereof and threadedly engaged with internal threads provided on an inner surface of the mounting bore, and an elastic membrane mounted to an inner end of the occluding member with one of opposite surfaces thereof facing the liquid passage and the other surface thereof facing a space defined between the elastic membrane and the occluding member, the occluding member being provided with a recess which opens into an inner end of the occluding member to define the space, an axially extending portion of the recess being disposed in the support tube portion within an axial region where the external threads are disposed.
With such arrangement of the twenty-fourth feature, the vibration generated in the vibration generating section induces the vibration of the liquid in the liquid passage, but a variation in pressure of the liquid is absorbed by flexing of the elastic membrane with its one surface facing the liquid passage. Thus, the exciting force applied from the liquid to the passage defining structure is effectively reduced, and the vibration sound radiated from the passage defining structure is reduced. Moreover, the vibration absorbing means is mounted to a portion of the outer wall of the passage defining structure and hence, the increase in weight of the passage defining structure due to the mounting of the vibration absorbing means can be suppressed to a small level to the utmost. In addition, the occluding member is provided with the recess opening into the inner end of the occluding member in order to define the space, and the volume of the space can be sufficiently ensured by the recess. Moreover, since the axially extending portion of the recess is disposed in the support tube portion within the axial region where the external threads, it is possible to avoid, to the utmost, that the portion for defining the space is disposed at a location axially offset from the support tube portion, thereby making the occluding member compact and reducing the weight of the occluding member by an amount corresponding to the provision of the recess.
According to a twenty-fifth aspect and feature of the present invention, there is provided a vibration sound reducing device comprising a vibration absorbing means which is mounted to a passage defining structure defining a liquid passage faced by at least a portion of a vibration generating section, the vibration absorbing means absorbing the vibration transmitted from the vibration generating section through a liquid in the liquid passage, wherein an outer wall of the passage defining structure is provided with a mounting bore which opens at an inner end thereof into the liquid passage, and the vibration absorbing means comprises an occluding member which is mounted to occlude the mounting bore and which includes a cylindrical support tube portion having external threads provided around an outer periphery thereof and threadedly engaged with internal threads provided on an inner surface of the mounting bore, and an elastic membrane mounted to an inner end of the occluding member with one of opposite surfaces thereof facing the liquid passage and the other surface thereof facing a space defined between the elastic membrane and the occluding member, the occluding member being provided with a tool-engaging bottomed bore which opens into an outer end of the occluding member, a recess which opens into an inner end of the occluding member to define the space, and a partition wall whose outer periphery is connected to an inner periphery of the support tube portion in a plane perpendicular to an axis of the mounting bore, the partition wall partitioning the tool-engaging bore and the recess from each other, opposite surfaces of the partition wall respectively defining a closed end of the tool-engaging bore and a closed end of the recess and being disposed on the support tube portion within an axial region where the external threads are disposed.
With such arrangement of the twenty-fifth feature, the vibration generated in the vibration generating section induces the vibration of the liquid in the liquid passage, but a variation in pressure of the liquid is absorbed by flexing of the elastic membrane with its one surface facing the liquid passage. Thus, the exciting force applied from the liquid to the passage defining structure is effectively reduced, and the vibration sound radiated from the passage defining structure is reduced. Moreover, the vibration absorbing means is mounted to a portion of the outer wall of the passage defining structure and hence, the increase in weight of the passage defining structure due to the mounting of the vibration absorbing means can be suppressed to a small level to the utmost. In addition, the occluding member is provided with the tool-engaging bore which opens into the outer end of the occluding member, and the recess which opens into the inner end of the occluding member in order to define the space. Thus, the occluding member can be screwed into the mounting bore by bringing a tool into engagement into the tool-engaging bore and turning the occluding member, and the volume of the space can be sufficiently ensured by the recess. Moreover, since the opposite surfaces of the partition wall defining the closed end of the tool-engaging bore and the closed end of the recess respectively are disposed on the support tube portion within the axial region where the external threads are disposed, portions of the tool-engaging bore and the recess are disposed within the axial threads are disposed. Thus, it is possible to avoid, to the utmost, that the tool-engaging bore and the recess are disposed at locations axially offset from the support tube portion, thereby making the occluding member compact, and further reducing the weight of the occluding member by an amount corresponding to the provision of the tool-engaging bore and the recess. Further, the rigidity of the support tube portion screwed into the mounting bore can be enhanced due to the outer periphery of the partition wall being connected to the inner periphery of the support tube portion.
According to a twenty-sixth aspect and feature of the present invention, in addition to the arrangement of the twenty-fifth feature, the partition wall is disposed at a central portion of the support tube portion within the axial region where the external threads are disposed. With such arrangement of the twenty-sixth feature, the rigidity of the support tube portion screwed into the mounting bore can be further enhanced.
The above and other objects, features and advantages of the invention will become apparent from the following description of the preferred embodiment taken in conjunction with the accompanying drawings.